Like many other languages, Japanese is ambiguous about the potential attachment sites of a relative clause which appears alongside a complex noun phrase. One important class of parsing theories (nondeterministic accounts) predicts that the relative clause will initially be attached to the first available host and later assigned to an alternative site, following the intervention of certain discourse processes. An alternative (deterministic) account maintains that the preliminary attachment site remains unchanged throughout the course of processing the sentence. The results of a questionnaire and a self-paced reading study with Japanese materials of this kind provided evidence of phased attachment first to one noun host and then to another. It is argued that these results are compatible only with nondeterministic accounts of parsing.